This disclosure generally relates to tools used in oil and gas wellbores. More specifically, the disclosure relates to drillable packers, pressure isolation tools and other tools used in deviated wells.
In the drilling and reworking of oil wells, a great variety of downhole tools are used. Such downhole tools often have drillable components made from metallic or non-metallic materials such as soft steel, cast iron or engineering grade plastics and composite materials. For example but not by way of limitation, it is often desired to seal tubing or other pipe in the well. It is desired to pump a slurry down the tubing and force the slurry out into a formation. The slurry may include for example fracturing fluid. It is necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well and likewise to force the slurry into the formation. Downhole tools referred to as packers, frac plugs and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas. Bridge plugs isolate the portion of the well below the bridge plug from the portion of the well thereabove such that there is no communication between the two well portions. Frac plugs, on the other hand, allow fluid flow in one direction but prevent flow in the other. For example, frac plugs set in a well may allow fluid from below the frac plug to pass upwardly therethrough but when the slurry is pumped into the well, the frac plug will not allow fluid flow therethrough so that any fluid being pumped down the well may be forced into a formation above the frac plug.
Wells drilled for the production of oil and/or gas often include a vertical portion and a deviated portion. The deviated portion is often horizontal or very nearly horizontal, and in some cases is past horizontal, so that it begins to travel upwardly toward the surface of the earth. The deviated section generally passes through the formation to be produced. The packer utilized to seal against the casing must be designed for the casing size in the deviated section of the well. Oftentimes, such wells will have different size casings. For example, the vertical section may have a larger diameter casing which will then transition to a small diameter casing which passes through the transition section, also referred to as a heel, into the deviated section of the well. In such cases, a tool, for example a packer designed for the horizontal section will pass through the larger section and then may be pumped around the heel into the horizontal section of the well.
There are circumstances, however, in which the larger diameter casing is installed not only in the vertical section of the well but in the transition section, or heel, and into the deviated section of the well. In such cases, a wire line cannot be used to lower the packer designed for the horizontal section into the horizontal section since the packer cannot be pumped around the heel into the horizontal section. Likewise, other tools, for example perforating guns, logging tools and other tools, if lowered on a wireline may not be pumped through a heel and into a smaller diameter casing in the deviated section of a heel. While coiled or stick tubing can sometimes be used, use of a wire line is quicker, easier and less expensive. Thus, there is a need for packers and pressure isolation tools that can be pumped through one casing size and into a smaller casing size for which the tool is designed and in which the tool will operate properly.